Mistakes 1 and 2: timing
Missing your Initial Enrollment Period earns permanent Part B and D penalties. Assuming employer coverage lets you delay, without confirming it qualifies, earns the same penalties with extra paperwork. Both die with one calendar reminder and one written confirmation from a benefits office.
Mistakes 3 and 4: assumptions
Picking a plan because a friend has it ignores that networks and drug lists are personal. Skipping drug coverage because you take nothing today ignores that the penalty for joining late runs forever, and that a bare-bones Part D plan is cheap insurance against next year.
Mistakes 5 and 6: set-and-forget
Never re-shopping your Part D plan quietly costs hundreds as formularies shift. Letting a Supplement premium creep for years without a quote check does the same. Both fixes are annual ten-minute reviews.
Mistake 7: going it alone
Medicare’s rules are written in federal register prose, and the people selling loudest on TV are not comparing every option in your county. Independent help is free and commission rules are set so that advice is not biased toward one carrier. Our founder wrote a book on exactly these mistakes; ask us for a copy, also free.